INFERIOR OOLITE AMMONITES. 



Ft. In. 



S o 

 a. .2 



A series of very variable beds, composed sometimes of ferruginous sand- 

 stone in thin layers which overlie calcareous beds containing shelly zones, 

 false-bedding being frequent; sometimes the whole section consists of 

 calcareous rock with false-bedding, sometimes it presents a series of 

 beds of compact ferruginous sandstone, with no fossils. In one 

 instance, the entire section consists of white sand and sandstone, with 

 no fossils ....... 



i. Coarse oolitic, or subcrystalline limestone with fossils, overlying a 

 calcareo-arenaceous slate like Collyweston Slate 



Beds, chiefly consisting of ironstone, containing Rhynchonella variabilis, 

 and JR. cynocephala ; and Ammonites bifrons 1 at the base 



Upper Lias Clay. 



30 



4 



35 



Part of the Beds No. 

 p. 370, as below. 



in the above section are more fully given by Mr. Sharpe at 



Part of Section of Old Duston Stonepit, using Quarrymen' s Terms. 



1. "The Yellow" building stone, consisting of six or seven beds of varying 



thickness, in two divisions, differing somewhat in tone of colour. These 



beds contain "pot-lids " of ironstone; also Cardium cognatum, &c. . 6-7 



2. " Best Brown Hard " building stone in three or four beds, — a coarser, 



stronger stone than that of the other beds, but of a rich red-brown 

 colour ; it contains few fossils . . . . .60 



C" 3. "Bough Bag," a slightly calcareous sandstone, green-hearted, hard, and 

 durable, used for copings, gravestones, and buildings. It contains 

 Ammonites Murchisonce, 2 A. opalinus, Nautilus, Geromya bajociana, 

 Pholadomya fidicula, Cardium cognatum, Cucullcea, &c, and a charac- 

 teristic zone of Astarte elegans . . . .30 



4. "Hard Blue," a very hard blue-hearted stone, the surfaces of the joints 



and bedding brown from oxidation. It contains the same fossils as the 



last bed excepting Ammonites MurcMsona and the Astarte elegans zone 3-4 



5. The presence of water prevents the working of the stone in this pit to a lower 



depth, but in an old disused pit in an adjoining field the beds for about 

 three feet lower are exposed, and these consist of cellular ironstone, 

 having sometimes green arenaceous, and sometimes ochreous cores . 3 



1 The occurrence of Am. bifrons is interesting to note when compared with the foregoing sections 

 of the Cotteswold Sands in Gloucestershire, Nos. V, VI, VIII. Mr. Thompson thinks the specimens 

 have come from Upper Lias nodules ; but this is not the case in the Cotteswolds. 



2 It must be understood that the list of species here given are merely copied from Mr. Sharpe's 

 paper, and rest on his authority. 



